Sorry I don't have a 205. On my 405 it is right on top of the engine and easy to spot. Functionally it provides a controlled air bypass round the throttle butterfly usually connected by hoses about 30mm diameter.
This is my 405 one
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Sometimes these are mistakenly called "stepper motors" but rarely are true stepper motors.
You can see some other examples by searching for "Idle control valve" on ebay current showing 633 but curiously none for a 205?
Yes you will have to dismantle to remove the valve - depending on where it is. I keep a spare in the car tucked under the drivers seat and swap mine in about 1 minute with no tools as it goes through periods of misbehaviour.
Looking at the history of your postings, I think you need to decide if the garage is going to maintain your car or you are going to do it yourself via advice here.
Firstly find your valve and determine how easy or otherwise it is to remove, then price up a new one and thirdly decide if you are going to do the job or pay someone else. Sorry to be blunt but .....
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